142 WILLIAM HARVEY 



have ventricles in the brain, whilst the goose has none. In 

 like manner, wherever the heart has a single ventricle, there 

 is an auricle appended, flaccid, membranous, hollow, filled 

 with blood; and where there are two ventricles, there are 

 likewise two auricles. On the other hand, some animals have 

 an auricle without any ventricle ; or, at all events, they have 

 a sac analogous to an auricle; or the vein itself, dilated at a 

 particular part, performs pulsations, as is seen in hornets, 

 bees, and other insects, which certain experiments of my 

 own enable me to demonstrate, have not only a pulse, but a 

 respiration in that part which is called the tail, whence it is 

 that this part is elongated and contracted now more rarely, 

 now more frequently, as the creature appears to be blown and 

 to require a large quantity of air. But of these things, more 

 in our "Treatise on Respiration." 



It is in like manner evident that the auricles pulsate, con- 

 tract, as I have said before, and throw the blood into the 

 ventricles; so that wherever there is a ventricle, an auricle 

 is necessary, not merely that it may serve, according to the 

 general belief, as a source and magazine for the blood: for 

 what were the use of its pulsations had it only to contain? 



The auricles are prime movers of the blood, especially the 

 right auricle, which, as already said, is "the first to live, the 

 last to die" ; whence they are subservient to sending the 

 blood into the ventricles, which, contracting continuously, 

 more readily and forcibly expel the blood already in motion ; 

 just as the ball-player can strike the ball more forcibly and 

 further if he takes it on the rebound than if he simply threw 

 it. Moreover, and contrary to the general opinion, neither 

 the heart nor anything else can dilate or distend itself so 

 as to draw anything into its cavity during the diastole, unless, 

 like a sponge, it has been first compressed and is returning to 

 its primary condition. But in animals all local motion pro- 

 ceeds from, and has its origin in, the contraction of some 

 part; consequently it is by the contraction of the auricles 

 that the blood is thrown into the ventricles, as I have already 

 shown, and from there, by the contraction of the ventricles, 

 it is propelled and distributed. Concerning local motions, it 

 is true that the immediate moving organ in every motion of 

 an animal primarily endowed with a motive spirit (as Aris- 





